The present invention addresses a problem with an OEM actuator for connecting the front wheel drive shaft to the front wheel hub. The OEM device is movable between engaged and disengaged positions through applying and removing air pressure. The OEM device is biased toward the disengaged position.
The OEM actuator the invention replaces is mounted on the back of the steering knuckle to provide a ring gear that will couple the hub and a half shaft. The half shaft is inserted into the actuator, where its splines are fully engaged with the ring gear until it becomes activated and engaged with the splines of the hub. The OEM actuator is vacuum controlled. To engage 4WD, the vacuum is released and a spring moves the ring gear to a position where it engages both the half shaft and the hub.
A typical OEM prior arrangement is shown in U.S. Pat. No. 6,318,533. FIG. 1 illustrates an exemplary prior art front drive wheel assembly that has a steering knuckle that is includes upper and lower mounts, A and B, and a wheel D on which a tire is mounted. The wheel D is driven through a half shaft E and a hub F which are powered by the outer race G of a constant velocity joint operatively associated with the half shaft E. There are a plurality of splines, H and I, which are selectively engageable through a locking collar J. The locking collar J is controlled by applying vacuum to the assembly K and collapsing the spring L which biases the assembly toward the two wheel drive mode. This vacuum actuation in the prior art is source of failure and intermittent operation.
The OEM actuator is prone to failure of the vacuum assembly and results in unexpected, erratic, or no 4WD engagement. Experience with the prior device has revealed a tendency for the OEM actuator to engage at inopportune times. Accordingly, it is desired to have a coupler that replaces the OEM actuator, eliminates the known failure points, and secures the half shaft and the hub in a fixed constant connection that does not rely upon any subsequent operation.